1. Field of Use
This invention relates generally to means to reduce oscillatory deflection of a vehicle, such as a rough-terrain type mobile crane, in which the vehicle chassis tends to oscillate angularly and vertically or "porpoise" and bounce relative to the terrain over which the vehicle travels because of terrain roughness or because of rapid acceleration or deceleration of the vehicle.
2. Description of the Prior Art
Some prior art vehicles used in construction work, such as rough-terrain type mobile cranes, for example, comprise a chassis having ground-engaging tires and a large heavy component, such as a pivotable telescopic crane boom mounted thereon. The tires typically take the form of large resiliently compressible inflated balloon tires, which may or may not be provided with additional resilient suspension springs between the wheel axles and the chassis. These tires (and axle springs, if any) serve as a resilient support means which enable the chassis to move vertically (bounce or porpoise) relative to the terrain. When driven from one job site to another, the crane boom is lowered into a road transport position and is usually secured to the chassis. Characteristically, when such a vehicle is driven over rough terrain or is accelerating or decelerating rapidly, the heavy chassis with the heavy boom thereon tends to oscillate angularly or "porpoise" relative to the terrain over which the vehicle travels. Such deflection, which occurs at some uncontrolled natural mode and frequency of vibration, is possible because of the resilient support provided by the tires and/or suspension springs. Such deflection is undesirable for several reasons. It can cause dangerous lack of driver control at road speeds and can even cause the vehicle wheels to momentarily leave the ground. Furthermore, it is uncomfortable and dangerous for the vehicle driver within the cab. It also imposes undesirable stressful vertical and torsional dynamic load on the wheel axles and other vehicle components. Then, too, it can cause the vehicle to damage the road surface.
Efforts have been made to solve the specific problem of vehicle bouncing as it pertains to trucks, as is shown by U.S. Pat. No. 2,744,749. Efforts have also been made to solve the general problem of system vibration as shown by U.S. Pat. No. 3,322,379. However, none of the teachings of these patents are applicable to overcome the above-described problems.